SB 608 
.W33 m 
Copy 1 



CONTROL OF 

WATERMELON ANTHRACNOSE 

BY SPRAYING 



F. C. MEIER 

Pathologist, Office of Cotton, Truck, and Forage Crop 
Disease Investigations 




Watermelon Anthracnose 



UNITED STATES DEPARTMENT OF AGRICULTURE 
DEPARTMENT CIRCULAR 90 



Contribution from the Bureau of Plant Industry 

( Office of Cotton, Truck, and Forage Crop Disease Investigations ) 

WM. A. TAYLOR, Chief 



Washington, D. C. 



March, 1920 



WASHINGTON t QOVERNMENT PRINTINQ OFFICE i 1920 



><«ii06T^|k 



WATERMELON ANTHRACNOSE has come to be 
recognized as a disease of major importance. 
This trouble annually causes an enorinous loss in our 
commercial watermelon territory, for the reason that 
when fields are attacked the yield is reduced and the 
quality of the fruit lowered. The disease occurs on 
other vine crops, among them the cucumber, musk- 
melon, and some varieties of gourds; consequently, 
it has come to be widely distributed. If the weather 
conditions are suitable, anthracnose is likely to occur 
in any section where watermelons are grown. The 
disease may cause loss to the farmer, transportation 
company, or distributor. This being the case, all 
parties concerned with the crop should cooperate in 
the introduction of control measures, the most im- 
portant of which is spraying. A good start was made 
in 1919, when more than 3,400 acres of watermelons 
were sprayed in Florida. There are some sections of 
the melon territory where spraying is already recog- 
nized as a necessary step in good melon culture, and 
it is believed that before long the practice will be 
rreneral. 



■'■■<y OF CONGRESS 

OCT 3 1933 



.VJ3^M4 



CONTROL OF WATERMELON ANTHRACNOSE 
BY SPRAYING/ 



Spray with Bordeaux mixture. 

When to spray 

How to spray 



CONTENTS 

Page 



Page. 

Preparation of Bordeaux mixture 7 

Nature of the disease 9 

General suggestions 11 



SPRAY WITH BORDEAUX MIXTURE. 

npHE MOST PRACTICABLE METHOD of reducing the dam- 

-*- age done by anthracnose is to spray the watermelon vines with 

1 1 50 Bordeaux mixture. If anthracnose spores are carried to 

healthy melon vines, they will become diseased unless protected by a 




Fig. 1. — Ineffectual spraying for watermelon anthracnose. This field was sprayed 
once with 1-4-50 Bordeaux mixture, which proved too weak to control the disease. 
Compare with figure 2. 

coating of spray mixture, which prevents the germination of these 
spores and the development of the fungus. (Figs. 1 and 2.) Thor- 
ough applications of Bordeaux mixture will prevent the spread of 
anthracnose and will help to control other diseases of the crop. 

^ This circular summarizes the results of a personal experience of four seasons in the 
watermelon territory, and it is believed that the methods outlined are applicable wher- 
ever anthracnose occurs. 

The writer wishes to acknowledge the assistance of the following men In the collection 
of information regarding spraying : H. B. Stevens and C. D. Sherbakoff, pathologists, 
Florida Agricultural Experiment Station, Gainesville, Fla. ; J. B. Berry, pathologist. Col- 
lege of Agriculture, Athens, Ga. ; M. L. Benn, C. M. Tucker, and A. H. Slocum, formerly 
field aids in plant pathology. Bureau of Plant Industry ; D. H. Gilbert, Monticello, Fla. ; 
G. H. Thorpe, Dry Branch, Ga. ; and C. B. Michelson, supervisor of farm marketing of 
the St. Louis-San Francisco Railroad. Much credit is dne the Melon Distributors' Associ- 
ation. This organization has taken an active interest in the disease-control work as a 
whole, and the members have rendered invaluable assistance by the dissemination of 
information with regard to spraying. 

168159°— 20 3 



4 Department Circular 90, U. S. Department of Agriculture. 



WHEN TO SPRAY. 

One must remember that spraying is a preventive, not a cure, and 
that it is effective only to the extent that the surface of the healthy 
plant is kept covered with a thin coating of the spray solution. 
Knowing this and the fact that the disease spreads rapidly during 
and immediately after rainy weather, the farmer must choose the 
j^roper time for the application. The following schedule will serve 
as a guide for making this selection : 

Make the first application when the vines begin to run. 

Spray the second time about one week after the first melons have *' set " 
on the vines. 

Make a third application about two weeks after the second. 

If anthracnose appears and the above schedule has not been used, 
try these emergency measures: Spray with Bordeaux mixture im- 
mediately and repeat the operation about 10 days later. If rains are 




Fig. 2. — A field in which the watermelon vines were sprayed five times with 4—4-50 
Bordeaux mixture. Tile foliage was heavy at shipping time and the melons were 
not spotted. 

frequent at this time a third spraying will probably be required. 
Cases have been known where it was necessary to spray during the 
loading period in order to secure a j^rofit from the crop. 

HOW TO SPRAY. 

THE SPRAY PUMP. 

The man who intends to spray his watermelons should prepare 
well in advance. ' A good spray pump should be secured, and his 
laborers should be made thoroughly familiar with the operation 
of the equipment. If the grower has a small acreage he may be 
able to unite with one or two neighbors in the purchase of a pump 
and materials. In order that sufficient pressure may be maintained 



Control of Watermelon Anthracnose by Spraying. 5 

gasoline-power equipment is almost essential for successful work 
with watermelons, although if the acreage is small, 10 or 15 acres, 
it may be necessary for purposes of economy to use a hand pump. 
Growers in certain sections of Florida and in central Georgia have 
found that the outfits used for spraying citrus fruits, pecans, and 
peaches may be adapted for use with watermelon vines. Orchard 
apparatus, however, is rather heavy for use in sandy fields. Several 
firms manufacture light gasoline-power outfits with the tanks 
mounted on two wheels, and these have many advantages for work 
with watermelons, particularly if stumps are abundant. (Figs. 3 
and 4.) In buying an outfit, care should be taken to secure all the 
clearance possible between the ground and the bottom of the tank. 
Since Bordeaux mixture contains copper sulphate the pump should 
be lined with brass or porcelain. 




Fig. 3. — Fining the spray tank in the field. This type of pump, in which the tank 
is mounted on two wheels, is manufactured by several companies. Such a machine 
is particularly well adapted for use where stumps are abundant. Time is saved 
by hauling the mixture to the field, so that the pump may be kept in continuous 
operation until the field is covered. A galvanized-iron bucket, like the one shown, 
should never be used for dipping Bordeaux mixture, as the mixture attacks iron. 
A wooden bucket should be used instead. 

EQUIP THE SPRAYER TO SUIT THE FIELD IN WHICH IT IS TO BE USED. 

The number and arrangement of leads of hose depend on the field 
in which they are to be used and the method of spraying. In gen- 
eral, the spray is applied by driving down a middle and spray- 
ing two or more rows on each side of the machine. (Fig. 5.) If 
the rows are 10 feet • apart and the vines are kept turned back 
throughout the season to give driveway in those middles that are 
to be used for this purpose, very little injury will be caused by 
the passage of the machine. Folding booms will usually be found 
useful to support the hose. In some cases, however, stumps and 
trees may be so abundant as to prevent the use of booms, in which 
case it will be necessary to employ boys to carry the hose in order 
to prevent injuring the vines. (Fig. 6.) 



6 Department Circular 90, U. S. Department of Agriculture. 

APPARATUS, SPRAYING MATERIALS, AND LABOR REQUIRED. 

The following outline has been prepared for the purpose of assist- 
ing the grower in the purchase of apparatus and supplies and in 
planning his work : 

(1) Gasoline-power spray pump, able to deliver the spray mixture to sis 
nozzles at 150 pounds pressure or more. The pump should be lined with brass 
or porcelain. 

(2) Three leads of §-inch hose, one 15 to 20 feet long behind the machine and 
the others each 30 feet long, extending one on each side of the machine and 
supported by a folding boom. Extra lengths of hose should be kept on hand. 

(3) Three 4 to 6 foot bamboo extension rods, each equipped with a faucet 
cut-off at the hose end and with Y fittings at the nozzle end. 

(4) Six angle (45°) disk nozzles, two for each extension rod. Extra nozzles 
should be kept on hand. 

(5) Four or more wooden barrels for use in mixing the solution. 

(6) Wooden buckets for dipping the bluestone solution. 

(7) A strainer for the Bordeaux mixture made of brass wire having 18 
meshes to the inch. 

(8) Copper sulphate (bluestone). 

(9) Quicklime (stone lime not air slaked). If necessary, hydra ted lime may 
be used. 




Fig. 4. — The pump in operation. As melons are frequently the first crop planted on 
new land, stumps are likely to be numerous. In such fields It is best to use a 
2-wheeled machine, with the greatest possible clearance between the ground and 
the tank. 

In ordering the spraying materials it is best to estimate in each 
case that about 4 pounds per acre will be required for each appli- 
cation. 

The force required to operate such an outfit as that recommended 
will consist of a driver, three men to apply the spray, and a team 
of mules or horses. (Figs. 7 and 8.) 

It is often convenient to have tAvo additional men for preparing 
the Bordeaux mixture. If this work is done at some distance from 
the field, time may be saved and wear on the sprayer avoided by 
having the mixture hauled to the field in barrels. Boys to carry the 
hose are necessary when the booms suggested are not used. 

If the outfit is handled effectively 25 to 50 acres and even more 
may be sprayed in one day. 



Control of Watermelon Anthracnose by Spraying. 7 

COST OF SPRAYING. 

In 1919 the cost of spraying an acre of melon vines once was about 
95 cents. This includes the cost of labor and materials, but does not 
take into account the depreciation of the machinery. 

PREPARATION OF BORDEAUX MIXTURE. 

In order that spraying may be accomplished in an effective and 
economical waj^ it is necessary that the application be made quickly 
as well as thoroughly-. Consequently, it is well worth while to pre- 
pare for mixing the solution in advance of the day on which the 
work is to be done by making stock solutions, from which the 
Bordeaux mixture can be prepared quickly. 

Purchase quicldime (not air slaked) and copper sulphate early 
in the season, in such quantities as to secure wholesale prices. Pro- 
vide wooden buckets for dipping the copper-sulphate and Bordeaux 
solutions and also four or more 50-gallon wooden barrels. These 
should be marked inside by driving several nails to indicate the 




Pig. 5. — The 4-wheeled sprayer shown in figure 2 in operation. Four men are required 
to handle the outfit. One drives, the man behind sprays the first row on each side 
of the machine, and the other two men the second and third rows, right and left, 
six rows in all. The man in the rear is applying the spray by directing it sidewise, 
holding the nozzle slightly above the foliage. This insures good penetration of the 
foliage. 

water line when containing 25 gallons of water. Then one or more 
days before spraying, make stock solutions of bluestone and lime, 
proceeding as follows: 

Place 25 gallons of water in a wooden barrel and dissolve 50 pounds of 
bluestone in this. This can be done conveniently by suspending a gunny sack 
containing the bluestone just below the surface of the water. About 24 hours 
will be required for the chemical to dissolve. Cover the barrel to prevent 
evaporation, or dilution in case of heavy rainfall. 

Slake 50 pounds or more of quicklime in a barrel or trough and keep this 
covered with water until time for using it. 

These stock solutions will make a sufficient quantity of Bordeaux 
mixture to cover about 12 acres of well-grown vines. If the acreage 



8 Department Circular 90, U. S. Department of Agriculture. 

is greater than this, larger quantities of the stock solutions should 
be prepared, using the proportions specified above. 
AA^ien ready to spray — ...j,;". ,,.. , 

(1) Pour 2 gallons of the copper-sulphate stock solution in a third barrel 
and add water to make 25 gallons. 

(2) In a fourth barrel, add about 6 pounds of slaked lime to 25 gallons of 
water and stir thoroughly. 

(3) Pour the two solutions through a strainer into the spray pump. • If 
a hand pump is used stir the mixture well ; if a power sprayer is used operate 
the agitator while running the mixture into the tank. 

The result of the above procedure will be 50 gallons of Bordeaux 
mixture, a sufficient quantity to cover about 1 acre of well-grown 




Fig. 



6. — A 4-wheeled power spraj'er rigged with three leads of hose. The home- 
made folding boom saves the expense of employing a boy to hold the hose. 



vines. If a large acreage is to be sprayed it is often found conven- 
ient to use larger barrels and to elevate these on a mixing platform 
in such a way that the stock solutions may be piped instead of 
dipped and the resulting dilutions allowed to run into the spray 
pump. 

In order to make sure that the copper sulphate is properly neutral- 
ized by the lime, Bordeaux mixture may be tested by what is known 
as the ferrocyanid test. An ounce of yellow prussiate of potash is 
dissolved in a pint of water, and a drop of this solution is allowed 
to fall on the surface of the spray mixture. If free copper is present 
the drop will immediately turn reddish brown in color. Lime milk 
should then be added until the brown color fails to appear. If the 
reaction is complete the yellow i>russiatc of j^otash solution will 
remain a clear yellow until it disappears into the mixture. 



Control of Watermelon Anthracnose by Spraying. 9 

NATURE OF THE DISEASE. 

APPEARANCE OF DISEASED VINES. 

Anthracnose is caused by a microscopic plant, a fungus known as 
CoUefotrichum lagenarium. Vines attacked by this fungus may be 
recognized by the numerous irregular black spots which appear on 
the leaves. When heavily infected, the foliage tends to shrivel and 
curl, and after a period of heavy rainfall, when the disease has 
spread rapidly, farmers often speak of their field as having been 




],-iQ_ 7. — ^v Bui'deaux mixing statiou. Tlie spray mixture slioukl be prepared in a 
place where water is readily accessible. It may then be hauled to the fleld and 
pumped or poured into the spray tank. A tank filler that may be attached to the 
pump is often a great saver of time and labor. 

" burned over," owing to the fact that the leaves in large areas have 
been crisped and blackened by the fungus. Many growers attribute 
the injury to excessive rainfall. This is in part true, as moist con- 
ditions are necessary for the growth and development of the fungus 
and consequent spread of the disease. If one examine diseased leaves 
carefully after a prolonged period of wet weather during which the 
leaf tissue has been kept moist, so that the fungus has had an 



10 Department Circular 90, U. S. Department of Agriculture. 

opportunity to develop, it is often possible to see an orange-pink 
layer partially covering the black spots. This is due to the presence 
of countless spores, microscopic fungous seed bodies, which spread 
the disease. 

APPEARANCE OF DISEASED FRUIT. 

Very young fruits when affected by the disease are likely to become 
deformed, and this is usually accompanied by the formation of 
irregular, black, sunken spots or light-green pimples with a yellow 
cast in the center. Pink spore masses often form on these at an 
early date. 

If infection does not occur until the melon has reached a weight 
of about 10 pounds or more the trouble is marked by small pimples 
or larger flattened elevations on the rind. These spots are often 
spoken of by farmers as " rain checks," " smallpox," " pock marks," 




Fig. S. — Hauling Bordeaux mixture to ttie field by truck. 

etc. When conditions are very moist in the field or when such melons 
are loaded and held for some time in a freight car bedded with wet 
straw or sawdust, these pimples become sunken and covered with 
masses of pink spores. Such spots often furnish a point of entrance 
to other organisms of decay. 

METHODS BY WHICH THE DISEASE IS SPREAD. 

There are numerous ways in which the spread of anthracnose may 
be accomplished. Spores may be spattered by raindrops to leaves 
near by or washed to the ground, where they are carried along to 
other plants by drainage water. Laborers often disseminate the 
disease, particularly if culls are removed or melons harvested while 
the vines are wet with dew or rain. Under such circumstances, spores 
are likely to be carried on hands and clothing from diseased vines 
to healthy ones. If spores lodge on the melon itself, the charac- 
teristic anthracnose lesions form. 



Control of Watermelon Anthracnose by Spraying. H 

EFFECT OF THE DISEASE ON YIELD. ' 

Assuming that there is for a start a single diseased vine in the 
field, the effect on the crop is largely dependent on weather condi- 
tions. Abundant rainfall leads to the rapid spread of the disease. 
If heavy rains prevail early in the season it is possible that the 
foliage will be completely destroyed before any fruit is matured. It 
is more often the case, however, that the trouble spreads rapidly 
shortly before or during the shipping time in a given locality, as 
this is likely to be a period when showers are frequent in the South- 
eastern States. Under these circumstances, much of the fruit shipped 
is removed from dead vines and is likely to be sunburned, severely 
spotted, and of inferior quality. In such cases the shipment may 
result in loss, not only to the grower but to the railroad and dealer 
as well. 

GENERAL SUGGESTIONS. 

Avoid introducing anthracnose and other diseases into the field 
on the seed. If the grower saves his own seed, a selection of disease- 
free seed stock should be made from healthy vines. 

Do not plant melons on the same land two years in succession. 
Not only anthracnose but other serious diseases live over from one 
season to another in the soil. 

Unless necessary, do not work among the vines when they are wet. 
This is a good time to spread disease if any is present. 

Select a bright, sunny day for spraying, in order that the mixture 
will dry thoroughly. 

If possible, avoid spraying when the heavy bloom is on, as great 
care must be taken at this time to avoid breaking off blossoms with 
the hose. 

Order quicklime and bluestone in advance. In an emergency 
hydrated lime, in amounts one-fourth to one-half greater than quick- 
lime, may be used. Bordeaux mixture so made should be tested with 
ferrocyanid of potash. Never use air-slaked lime. 

Make the Bordeaux mixture carefully. If it contains more than 
4 pounds of bluestone to 50 gallons the foliage may be severely 
burned. Never use an old mixture. The spray must be prepared 
fresh just before it is used. 

It has been the writer's experience that homemade Bordeaux mix- 
ture is more satisfactory for spraying watermelons than any of the 
commercial preparations. If one intends to use prepared Bordeaux 
mixture it is desirable to know the strength and also the value of the 
preparation in terms of cost of materials. Farmers Bulletin 994, 
entitled " Commercial Bordeaux Mixtures : How to Calculate Their 
Values," should be read in this connection. 

Always wash out the equipment with water after spraying. 

o 



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